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Improve lazy loaded Singleton example

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This commit is contained in:
Ilkka Seppälä 2020-06-10 18:10:34 +03:00
parent e68beb40ec
commit 3033e4c9fc
1 changed files with 8 additions and 7 deletions
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15
singleton/src/main/java/com/iluwatar/singleton/ThreadSafeLazyLoadedIvoryTower.java
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@ -27,15 +27,13 @@ package com.iluwatar.singleton;
* <p>Thread-safe Singleton class. The instance is lazily initialized and thus needs synchronization
* mechanism.</p>
*
* <p>Note: if created by reflection then a singleton will not be created but multiple options
* in the same classloader</p>
*/
public final class ThreadSafeLazyLoadedIvoryTower {
private static ThreadSafeLazyLoadedIvoryTower instance;
private static volatile ThreadSafeLazyLoadedIvoryTower instance;
private ThreadSafeLazyLoadedIvoryTower() {
// protect against instantiation via reflection
// Protect against instantiation via reflection
if (instance == null) {
instance = this;
} else {
@ -44,13 +42,16 @@ public final class ThreadSafeLazyLoadedIvoryTower {
}
/**
* The instance gets created only when it is called for first time. Lazy-loading
* The instance doesn't get created until the method is called for the first time
*/
public static synchronized ThreadSafeLazyLoadedIvoryTower getInstance() {
if (instance == null) {
instance = new ThreadSafeLazyLoadedIvoryTower();
synchronized (ThreadSafeLazyLoadedIvoryTower.class) {
if (instance == null) {
instance = new ThreadSafeLazyLoadedIvoryTower();
}
}
}
return instance;
}
}